Apparatus and method for molten glass flow control along an isopipe weir

ABSTRACT

An apparatus for fusion draw glass manufacture, including at least one isopipe ( 110 ) having at least one weir ( 114 ); and a fluid discharge member in proximity to the at least one weir ( 114 ) of the at least one isopipe ( 110 ), the fluid discharge member is in fluid communication with a remote fluid source. The fluid source can be a source of a gas, liquid, solid or radiation. The fluid can be heated or cooled. At least one of the temperature properties, flow properties and thickness properties of the molten glass can be locally changed with the discharged fluid. A method of forming a glass-glass laminate sheet and uses of the laminate sheet are disclosed.

This application claims the benefit of priority to U.S. ProvisionalApplication No. 61/817545 filed Apr. 30, 2013 the content of which isincorporated herein by reference in its entirety.

The entire disclosure of any publication or patent document mentionedherein is incorporated by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to commonly owned and assigned U.S. Pat. No.8,007,913, issued Aug. 30, 2011, to Coppola, et al., entitled “LaminatedGlass Articles and Methods of Making Thereof”; U.S. Ser. No. 13/479701,filed May 24, 2012, to Coppola, et al., entitled “Apparatus and Methodfor Control of Glass Streams in Laminate Fusion”; and U.S. Ser. No.61/676028, filed Jul. 26, 2012, to Kersting, et al., entitled“Refractory Liner Structure and Use in Glass Fusion Draw”; and U.S. Ser.No. 61/678218, filed Jul. 8, 2012, to Coppola, et al., entitled “Methodand Apparatus for Laminate Fusion,” which content is relied upon andincorporated herein by reference in its entirety, but does not claimpriority thereto.

BACKGROUND

The disclosure generally relates to an apparatus and method for fusionglass manufacture or laminate fusion glass manufacture.

SUMMARY

The disclosure provides an apparatus and method for localized flowcontrol of the molten glass mass (i.e., glass stream(s)) at or along theweirs of an isopipe using a fluid stream projection from a source ontothe molten glass.

BRIEF DESCRIPTION OF DRAWINGS

In embodiments of the disclosure:

FIGS. 1A and 1B show, respectively, cross-section and side-viewschematics of a PRIOR ART laminated glass forming apparatus and process.

FIG. 2 shows a top view schematic of a clad isopipe and its weirs.

FIGS. 3A and 3B show respectively, a side view and top view of anexemplary fluid or air jet arrangement or fluid jet array directed overa weir of a core or clad isopipe.

FIG. 4 is a graph that shows thickness change vs. fluid air-jet angularorientation as a function of fluid air jet flow rates.

DETAILED DESCRIPTION

Various embodiments of the disclosure will be described in detail withreference to drawings, if any. Reference to various embodiments does notlimit the scope of the invention, which is limited only by the scope ofthe claims attached hereto. Additionally, any examples set forth in thisspecification are not limiting and merely set forth some of the manypossible embodiments of the claimed invention.

In embodiments, the disclosed apparatus and the disclosed apparatus andmethod of using the apparatus provide one or more advantageous featuresor aspects, including for example as discussed below. Features oraspects recited in any of the claims are generally applicable to allfacets of the invention. Any recited single or multiple feature oraspect in any one claim can be combined or permuted with any otherrecited feature or aspect in any other claim or claims.

Definitions

“Include,” “includes,” or like terms means encompassing but not limitedto, that is, inclusive and not exclusive.

“About” modifying, for example, the quantity of an ingredient in acomposition, concentrations, volumes, process temperature, process time,yields, flow rates, pressures, viscosities, and like values, and rangesthereof, or a dimension of a component, and like values, and rangesthereof, employed in describing the embodiments of the disclosure,refers to variation in the numerical quantity that can occur, forexample: through typical measuring and handling procedures used forpreparing materials, compositions, composites, concentrates, componentparts, articles of manufacture, or use formulations; through inadvertenterror in these procedures; through differences in the manufacture,source, or purity of starting materials or ingredients used to carry outthe methods; and like considerations. The term “about” also encompassesamounts that differ due to aging of a composition or formulation with aparticular initial concentration or mixture, and amounts that differ dueto mixing or processing a composition or formulation with a particularinitial concentration or mixture. The claims appended hereto includeequivalents of these “about” quantities.

“Optional” or “optionally” means that the subsequently described eventor circumstance can or cannot occur, and that the description includesinstances where the event or circumstance occurs and instances where itdoes not.

“Consisting essentially of” in embodiments can refer to, for example:

An apparatus for fusion draw glass manufacture, consisting essentiallyof:

one or a plurality of isopipes, each isopipe having at least one weir;and

one or a plurality of fluid discharge members in proximity to the atleast one weir of the isopipe, the fluid discharge member or membersbeing in fluid communication with a remote fluid source.

A method for controlling the glass streams in fusion glass manufacturein the above mentioned apparatus, consisting essentially of:

flowing molten glass over the at least one weir of the at least oneisopipe; and

discharging the fluid from the fluid discharge member in proximity tothe at least one weir of the at least one isopipe onto the molten glassflowing over the at least one weir of the isopipe.

A method for controlling the glass streams in fusion glass manufacturein the above mentioned apparatus, consisting essentially of:

characterizing the thickness defect profile of a fusion glassmanufacture product by measuring the glass thickness across the draw anddown the draw;

determining at least one fluid discharge configuration that remedies,that is, partially or substantially reduces the thickness defectprofile, wherein the at least one fluid discharge configuration includesat least one of:

the fluid flow rate and relative temperature difference between thefluid and the glass stream;

the orientation of the at least one fluid discharge member with respectto the inlet and compression ends of the isopipe;

the location or proximity of the at least one fluid discharge memberwith respect to the inlet end and compression end of the isopipe;

the geometry of the at least one fluid discharge member;

or combinations thereof; and

discharging a gaseous fluid from the fluid discharge member to the atleast one weir of the at least one isopipe onto the molten glass flowingover the at least one weir of the isopipe in accordance with thecharacterized thickness defect profile and the determined at least onefluid discharge configuration.

The apparatus and the method of using the apparatus of the disclosurecan include the components or steps listed in the claim, plus othercomponents or steps that do not materially affect the basic and novelproperties of the compositions, articles, apparatus, or methods ofmaking and use of the disclosure, such as a particular apparatusconfiguration, particular additives or ingredients, a particular agent,a particular structural material or component, a particular irradiationor temperature condition, or like structure, material, or processvariable selected.

The indefinite article “a” or “an” and its corresponding definitearticle “the” as used herein means at least one, or one or more, unlessspecified otherwise.

Abbreviations, which are well known to one of ordinary skill in the art,may be used (e.g., “h” or “hrs” for hour or hours, “g” or “gm” forgram(s), “mL” for milliliters, and “rt” for room temperature, “nm” fornanometers, and like abbreviations).

Specific and preferred values disclosed for components, ingredients,additives, dimensions, conditions, and like aspects, and ranges thereof,are for illustration only; they do not exclude other defined values orother values within defined ranges. The apparatus and methods of thedisclosure can include any value or any combination of the values,specific values, more specific values, and preferred values describedherein, including explicit or implicit intermediate values and ranges.

In a traditional fusion draw process, glass stream or layer thicknessdeviations can be corrected by mechanical adjustments at the root orlower tip of the isopipe and can affect the bulk glass but withoutdiscriminating the individual glass layers (see for example, U.S. Pat.No. 3,338,696, to Dockerty). In a multi-layer lamination, the thicknessof each glass layer is preferably controlled to specified tolerances.Thus, an additional method to independently control the thicknessproperties or thickness profile of each of the glass layers would bevaluable.

In embodiments, the disclosure provides an apparatus and method forcontrolling the glass streams in laminate fusion glass manufacture. Moreparticularly, the disclosure provides an apparatus and method forcontrol of molten glass mass flow properties along an isopipe weir in afusion draw process by selectively contacting the overflow molten glassmass with a fluid source at a temperature other than (e.g., cooler orhotter) the temperature of the molten glass mass.

In the laminate double-fusion forming (LDF) process, both weirs of theupper clad isopipe can be contacted with or made accessible to, forexample, the highly localized heating or cooling sources. These sourcescan be used to create localized temperature perturbations in the glassalong the line of the weir.

An example source is a single air jet that blows, for example, localizedcold air on top of the glass flowing atop of or over a weir. Inembodiments, an array of air jets, or like source and dispense ordischarge member instrumentalities, can be distributed along the weirline of either or both weirs. If each source such as an air jet'scharacteristic “width” is not too large, then an array of air jets canbe used to alter the glass mass flow distribution over a particular weirin a predictable way and as called for in process control.

The disclosure relates primarily to laminate fusion draw sheet making,in particular, three layer thickness control. However, one skilled inthe art will recognize the disclosure can also be readily applied toother draw processes for a variety of purposes.

In embodiments, the disclosure provides a fusion draw apparatus havingan isopipe and a fluid source dispenser or discharger in proximity to atleast one weir of at least one isopipe.

In embodiments, the fluid source can be configured to discharge fluidonto the surface of the molten glass overflowing the weir. Thedischarged fluid can locally change the temperature and the flowproperties of the molten glass overflowing the weir. The changed flowproperties can be used to change the thickness of the molten glassstream overflowing the weir and consequently the thickness of therespective glass layer or layers in the resulting fusion draw glassribbon and sheet of the resulting laminate glass ribbon.

In embodiments, each fluid source delivery member, such as a tube, canbe, for example, independently or dependently oriented, moved, oradjusted, with respect to the other tubes in an array of tubes. Inembodiments, the tubes delivering the fluid source to the surface of theglass overflowing the isopipe weir can be used to control thetemperature properties of the glass stream and the resulting thicknessesproperties of the resulting glass ribbon.

In embodiments, the fluid source delivery member or discharger can beoriented at the same or different directions with respect to the surfaceor edge of the weir. In embodiments, the fluid source delivery ordischarger member can be oriented or reoriented manually or robotically.In embodiments, the fluid source delivery member or discharger can beoriented or reoriented remotely, for example, by mechanical means orrobotic means. In embodiments, the fluid source delivery member ordischarger can be, for example, at least one tube, such as a pluralityof tubes or an array of tubes. In embodiments, each tube in a pluralityof tubes can be oriented individually or independently of the othertubes. In embodiments, each tube in a plurality of tubes can be orientedsubstantially identically to the other tubes in an array of tubes andcan be situated, for example, in a line or linearly, and in closeproximity to at least one weir of an isopipe, such as from about 0.1 mmto about 20 mm, and like values, including intermediate values andranges.

In embodiments, the disclosure provides an apparatus for fusion drawglass manufacture, comprising:

at least one isopipe having at least one weir; and

a fluid discharge member or discharger in proximity to the at least oneweir of the at least one isopipe, the fluid discharge member ordischarger is in fluid communication with a remote fluid source.

In embodiments, the fluid source can be, for example, a source of atleast one of a gas, a liquid, a solid, radiation, or combinationsthereof.

In embodiments, the gas can be, for example, a heated or cooled gas suchas air, nitrogen, argon, and like gases, or combinations thereof. Theliquid can be, for example, a heated or cooled liquid such as water, analcohol, a glycol, and like liquids, or combinations thereof. The solidcan be, for example, a heated or cooled solid such as a wax, a talc, apowder, dry ice (CO₂) particles or dust, and like solids, orcombinations thereof. The radiation can be, for example, any actinicsource of an energetic beam such as UV, visible, IR, X-ray, microwave,and like sources, or combinations thereof. One source of an energeticbeam is a laser or combination of lasers.

In embodiments, the fluid discharge member delivers a heated fluid, acooled fluid, or combinations thereof, to the surface area of a moltenglass mass (i.e., the work piece) stream overflowing the at least oneweir.

In embodiments, the fluid discharge can be accomplished selectively withrespect to, for example, the position, such as the location, on thesurface of molten glass overflowing the weir, and the relativeorientation, that is, the direction or directions of the fluid dischargeonto the surface of molten glass overflowing the weir of the isopipe.

In embodiments, the fluid source can include a fluid discharge member,such as tube, nozzle, hose, and like structures, or combinationsthereof. The fluid discharge member communicates the temperatureconditioned fluid from the fluid source to the surface point or area ofthe molten glass overflowing the weir. In embodiments, a fluid dischargemember can be oriented in different directions with respect to thesurface or edge of the weir. In embodiments, the fluid discharge membercan be oriented or reoriented manually or robotically using, forexample, mechanical linkages situated inside or outside of the heatedenclosure, such as a muffle, a doghouse, or both, surrounding theisopipe(s). In embodiments, the fluid discharge member can be orientedor reoriented remotely. In embodiments, the fluid discharge member canbe, for example, at least one tube, such as a single tube, a pluralityof tubes, or an array of tubes. In embodiments, each tube in a pluralityof tubes can be oriented individually or independently of the othertubes. In embodiments, each tube in a plurality of tubes can becoordinatively oriented substantially identically or in tandem (e.g., agroup of two or more fluid discharge member arranged side-by-side oracting in conjunction with) to the other tubes in an array of tubes. Thearray of tubes can situated, for example, in a line or linearly, and inclose proximity to the glass stream overflowing at least one weir of anisopipe. The close proximity of fluid discharge member with respect toat least one weir of an isopipe can be, for example, from about 0.1 cmto about 20 cm, from about 0.2 cm to about 10 cm, from about 0.3 cm toabout 5 cm, from about 0.5 cm to about 2 cm, and like close proximitydimensions, including intermediate values and ranges.

In embodiments, each discharge member such as the tubes in array oftubes can be, for example, independently or dependently moved oradjusted with respect to the other tubes in an array. In embodiments,the tubes delivering the fluid to the surface of the glass overflowingthe isopipe weir can be used to control the temperature properties ofthe glass stream, and consequently, the resulting thicknesses propertiesof the resulting glass ribbon, including the thickness of individuallayers in a laminate glass ribbon having two or more layers.

In embodiments, the fluid discharge member discharges a fluid from thefluid source to at least one location on the surface of molten glassoverflowing the at least one weir, for example, a single location, twolocations, a continuous line, a discontinuous line, a plurality ofsimilar locations, a plurality of dissimilar locations, or combinationsthereof, on the surface of molten glass overflowing the at least oneweir.

In embodiments, the fluid discharge member discharges a fluid in atleast one direction or orientation on the surface of molten glassoverflowing the at least one weir, for example, a single direction ororientation, two different directions or different orientations, or aplurality of different directions or different orientations on thesurface of molten glass overflowing the at least one weir.

In embodiments, the fluid discharge member discharges a fluid that can,for example, locally change: the temperature properties of the moltenglass overflowing the weir; the flow properties of the molten glassoverflowing the weir; the thickness properties of the molten glassstream overflowing the weir; or a combination thereof.

In embodiments, the fluid discharge member discharges a fluid streamselected from at least one of: a point; a small spot; a large spot; anoval, a non-symmetrical ellipsoid or egg shape profile, a parabola, anhyperbola, a triangle or wedge shaped profile, or combinations thereof.

In embodiments, the fluid discharge member can be, for example, a tube,a pipe, an air knife, an air curtain, and like members, or combinationsthereof.

In embodiments, the disclosed apparatus can further comprise, forexample, an enclosure that substantially surrounds the at least oneisopipe having at least one weir and the fluid discharge member, forexample, a muffle, a doghouse, and like enclosures, or combinationsthereof.

In embodiments, the disclosure provides a method for controlling theglass streams in fusion glass manufacture in the above mentionedapparatus, comprising, for example:

-   -   flowing molten glass over the at least one weir of the at least        one isopipe; and    -   discharging a fluid from the fluid discharge member or        discharger situated in proximity to the at least one weir of the        at least one isopipe onto the molten glass flowing over the at        least one weir of the isopipe.

In embodiments, discharging a fluid from the fluid discharge member canbe accomplished, for example, selectively to specified positions atopthe weir overflow, such as one or more locations, spots, lines, regions,or combinations thereof.

In embodiments, discharging a fluid from the fluid discharge member canbe accomplished, for example, by discharging an array of fluid dischargemembers that have the same spatial orientation and direction.

In embodiments, discharging a fluid from the fluid discharge member canbe accomplished, for example, by discharging an array of fluid dischargemembers having at least one fluid discharge member having a differentspatial orientation, direction, or both, compared to the other fluiddischarge members in the array.

In embodiments, the disclosure provides a method for controlling theglass streams in fusion glass manufacture in the above mentionedapparatus, comprising:

-   -   characterizing the thickness defect profile of a fusion glass        manufacture product;    -   determining at least one fluid discharge configuration, for        example, experimentally, modeling, simulation, or a combination        thereof, which configuration remedies the thickness defect        profile, and the at least one fluid discharge configuration        comprises at least one of:        -   the fluid flow rate and relative temperature difference            between the fluid and the glass stream;        -   the orientation of the at least one fluid discharge member            with respect to the inlet and compression ends of the            isopipe;        -   the location or proximity of the at least one fluid            discharge member with respect to the inlet and compression            ends of the isopipe;        -   the geometry of the at least one fluid discharge member, for            example, a fluid discharger having a nozzle or like tip            having, for example, a circular, a flared, an angled, a            slotted, and like opening geometries, or combinations            thereof;        -   or combinations thereof; and    -   discharging the fluid from the fluid discharge member to the at        least one weir of the at least one isopipe onto the molten glass        flowing over the at least one weir of the isopipe in accordance        with the characterized thickness defect profile and the        determined at least one fluid discharge configuration.

The disclosed apparatus and method are advantaged, for example, byproviding the ability to:

-   -   independently alter the glass flow distribution that flows over        either the left or the right weir of a fusion isopipe (such a        capability enables the thickness of the three layers or higher        multi-layers of a laminated glass sheet product to be        independently controlled);    -   create complex thickness patterns (e.g., clad-layers only, and        where right side clad thickness is asymmetrical or not a mirror        image of left side clad thickness);    -   alter the molten glass mass flow at the ends of a single fusion        isopipe to influence, for example, bead thickness, sheet width        variation to combat isopipe sag, or a combination thereof; and    -   alter the molten glass mass flow over the quality area of a        single fusion isopipe to control thickness of the single layer        provides an alternative or compliment to a known mechanical        thickness control method (see U.S. Pat. No. 3,338,696, to        Dockerty, supra).

Laminated glass sheets can have, for example, three layers consisting ofan inner core glass layer, and two outer clad glass layers. The coreglass is sourced from a single isopipe where the glass flow on each sideof the isopipe fuse at the root or base of the isopipe to form onehomogenous glass layer. The clad glass is also sourced from one isopipebut the glass flow on each side of the isopipe is deposited on the outersurface of the glass layer flowing on the same side of the core isopipeto form two layers on the outside of the final laminated glass sheet(see FIG. 1).

The thickness (i.e., average value and uniformity across the sheet) ofeach glass layer is preferably controlled to specified tolerances. Inembodiments, the present disclosure provides a method that uses a singleisopipe, and a single layer fusion forming process to control theoverall or total thickness of the laminated sheet in combination with anew device(s) and method that allows the thickness of each of the twoclad glass layers to be controlled independently.

Generally glass thickness properties are very stable in the vertical ordown-the-draw direction. Thickness uniformity or control address in thepresent disclosure is, in embodiments, directed to the less stable andless easily controlled horizontal or across-the-draw direction.

EXAMPLE(S)

The following examples serve to more fully describe the manner of usingthe above-described disclosure, and to further set forth best modescontemplated for carrying out various aspects of the disclosure. Theseexamples do not limit the scope of this disclosure, but rather arepresented for illustrative purposes. The working example(s) furtherdescribe(s) the apparatus and method of using the apparatus of thedisclosure.

Referring to the Figures, FIGS. 1A and 1B show, respectively, a crosssection (FIG. 1A) and a side view (FIG. 1B) of laminated glass formingapparatus and process having a core isopipe (105) surmounted by a cladisopipe (110). The core isopipe (105) provides and directs the coreglass stream (107). The clad isopipe (110) provides and directs the cladglass stream (112) onto the core glass stream (107). The clad isopipe(110) includes a trough (113) and a first weir (114 a) and a second weir(114 b), which weirs can act as partial dams or gates that can permitcontrol or regulation of the molten clad glass stream (112) over flowand the thickness of the resulting respective clad layers.

FIG. 2 shows a top view schematic of the clad isopipe trough (113).Molten glass flows generally from the left inlet (202) side to rightcompression (204) side of the trough (113), although as a fluid elementor discharger, such as an air jet stream, provides a glass stream path(115), approaches either weir the molten glass trajectory, in cooling,tends to become abbreviated or shortened so as to approach a moreperpendicular orientation or trajectory such as a glass stream path(118). The directional axes (0°, 90°, 180°, 270°) in the upper left ofthe figure provide the air-stream angle (210) convention as thedischarger projects into the plane of the glass stream surfaceoverflowing the weirs (114 a; 114 b).

FIGS. 3A and 3B shows aspects of an example of the disclosed apparatusand method having an air jet arrangement of dischargers directed over aweir of a clad isopipe (110). FIG. 3A is a side view of the clad pipeshowing an array of air jets (310) comprised of one or more tubes ornozzles that can be distributed, for example, along a top line runningfrom the inlet (202) end to the compression (204) end of both weirsurfaces (114). In embodiments, the fluid nozzle jet, or tube such asnozzle (116) can have broad (117) or narrow (119) contact pattern withthe glass (305) surface. FIG. 3B is a top view showing alternativeangular orientations for one tube (320) of the array at 0 degrees(pointing left or 9 o'clock), 90 degrees (pointing down or 6 o'clock),and 180 degrees (pointing right or 3 o'clock). In this example the tipof the air jet is bent to form an angle that allows the air stream tohit the top surface of the molten glass at an angle less than, forexample, 90 degrees but typically greater than, for example, 45 degrees.This particular arrangement allows each jet or tube of the array (310)to be aimed by varying, for example, the angle of rotation, the heightof the tube above the glass surface, or both. Other types of jet sourceequivalents or variations that can be used can include, for example:hot-air jets; gasses other than air; radiation based heating or coolingsources, such as focused or collimated; and other tube spatialarrangements. Alternative exemplary nozzle angular orientations (e.g.,325 a, 325 b, 325 c) and associated fluid streams (119) are available.

The fluid or air jet stream can act to cool the glass locally, forexample, at the point or points of contact of the air stream with theglass, and thus reduce the glass mass flow that would follow the glassstream lines (see, e.g., FIG. 2 lines 115) from the point of contact tothe point where the glass mass flow overflows the weir. In embodiments,where there is greater the cooling of the glass stream by the appliedfluid stream the glass stream lines can become shorter, e.g., typicallyhaving greater viscosity, less flow, reduce flow length (see, e.g., FIG.2, lines 118), and a greater cross-sectional thickness.

FIG. 4 shows the relationship of thickness change vs. air stream angularorientation and air jet flow. Specifically, FIG. 4 graphically shows theeffect of the air stream impact point, contact point, region of contactor impact, and the fluid (e.g., air) flow rate in standard cubic feetper hour (SCFH) on the thickness of a glass ribbon. In this scenario,one air jet with a bent-tip as described above (e.g., the air-streamangle to glass surface is about 60 degrees) was positioned (from 20 to200 mm) over one weir (about mid-way between inlet and (left) andcompression end (right)) of a small (about 254 mm wide) fusion isopipe.The air-stream angle (see FIG. 2, 210 for fluid source orientationconvention with respect to the top view of the weir and analogous to acompass heading) was varied along with the air flow rate and theresulting glass sheet thickness was measured with a laser gauge. Thenominal thickness of the glass sheet was about 2.8 mm so the maximumchange of about 0.2 mm observed is nearly 7% of nominal This is arelatively large range with respect to potential control capability.

The air-stream angle can change the location of maximum influence onthickness in a predictable way relative to the glass sheet. For example,reducing the air flow from an air jet tends to reduce the degree of“thinning” also in a predictable, monotonic way. The maximum influenceposition can also be changed by raising or lowering an air jet (e.g., atube) where raising the air jet effectively reduces flow and cooling anddecreases thickening, whereas lowering the air jet increases flow andcooling and increases thickening.

Although not limited by theory, the following enumerated instances orsituations describe conditions and methods that may or may not call forapparatus or system modification for controlling glass flow andthickness properties.

A first ideal situation is where the glass mass flow distribution overeach of the four weirs (i.e., two weirs of the core pipe and two weirsof the clad pipe) is highly uniform and symmetric from left side toright side. This situation essentially calls for no system thicknessadjustment or thickness adjustment method.

A second, less than ideal situation is where the ratio of clad glass tocore glass on both sides of the fusion machine is everywhere the same,but where the combined thickness of all three layers varies from theisopipe inlet end to the isopipe compression end (and for example, withseveral undulations about a best fit line). This situation can use theconventional isopipe tilting method (see U.S. Pat. No. 3,338,696, toDockerty, supra, or see for example, the above mentioned copending U.S.Ser. No. 61/678218) to adjust the overall thickness as needed.

A third situation is similar to the second situation but where the ratioof clad to core glass is not the same on one side of the fusion machinerelative to the other side. In this situation it is possible thatadjustments of the “roll” or “cross-tilt” of either one or both isopipesmay be enough to reduce the problem to the first or the second type.

In a fourth situation the ratio of clad to core glass varies smoothlyfrom the isopipe inlet end to the compression end on both sides (and inthe same way) of the isopipe. In this situation it is possible thatadjustments of the “uptilt” or “downtilt” of either one or both of theisopipes may be enough to reduce the problem to the above mentionedfirst or second situations.

In a fifth situation, there can be a combination of the third and fourthsituations, which fifth situation can be addressed with a combination ofisopipe movements to again reduce the problem to the above mentionedfirst or second situations.

Finally for the more general, sixth situation, the problem of threelayer thickness control, a method to control the overall thicknesscombined with a method to independently control the mass flowdistribution on both sides of the clad isopipe can be used. If thethickness of the individual layers of a three layer glass sheet can bemeasured precisely enough, then a system such as shown in FIG. 3 can beused to adjust the mass flow distribution on both sides of the cladisopipe so that the resulting three layer thickness control problemreduces to any of the situations 1 to 5 described above. The“resolution” of the disclosed apparatus and method can be, for example,the highest frequency of thickness errors that the system can correct.The single tube responses from FIG. 4 are about 50 to 70 mm wide in thevicinity of their maximum impact. For the standard system (see U.S. Pat.No. 3,338,696, to Dockerty, supra) the characteristic width is nearly254 mm wide. The smaller that this characteristic width is, the higherthe inherent resolution. It is unlikely that thickness performance ofthe resulting three layer laminated glass sheet will be limited by aninability to control clad glass mass flow distribution to a suitablyhigh degree of resolution.

In embodiments, the disclosure provides a method of forming aglass-glass laminate sheet comprising:

flowing a first molten glass over a first weir of a first isopipe toform a first molten glass stream;

flowing a second molten glass over a second weir of a second isopipe toform a second molten glass stream;

forcing a fluid from a fluid discharge member in proximity to at leastone of the first and second weirs such that the fluid is directed ontothe respective molten glass stream; and

fusing the first and second molten glass streams to each other to form amultilayer glass-glass laminate sheet.

In embodiments, the disclosure provides for a use of the multilayerglass-glass laminate sheet, made by the above preceding method, as acover glass or a glass backplane in an electronic device.

In embodiments, the disclosure provides for a use of the multilayerglass-glass laminate sheet, made by the above preceding method, in anLCD display, an LED display, a computer monitor, an automated tellermachine (ATM), a mobile telephone, a personal media player, a tabletcomputer, a photovoltaic component, an architectural glass pane, anautomotive glazing, a vehicular glass, a commercial appliance, ahousehold appliance, or a solid state lighting article.

In embodiments, the disclosure provides for a glass article formed usingthe apparatuses or methods described herein to be used for a variety ofapplications including, for example, for cover glass or glass backplaneapplications in consumer or commercial electronic devices including, forexample, LCD and LED displays, computer monitors, and automated tellermachines (ATMs); for touch screen or touch sensor applications; forportable electronic devices including, for example, mobile telephones,personal media players, and tablet computers; for photovoltaicapplications; for architectural glass applications; for automotive orvehicular glass applications; for commercial or household applianceapplications; or for lighting applications including, for example, solidstate lighting (e.g., luminaires for LED lamps).

The disclosure has been described with reference to various specificembodiments and techniques. However, it should be understood that manyvariations and modifications are possible while remaining within thescope of the disclosure.

1. An apparatus for fusion draw glass manufacture, comprising: at leastone isopipe having at least one weir; and a fluid discharge member inproximity to the at least one weir of the at least one isopipe, thefluid discharge member is in fluid communication with a remote fluidsource.
 2. The apparatus of claim 1 wherein the fluid source comprises asource of at least one of a gas, a liquid, a solid, radiation, orcombinations thereof.
 3. The apparatus of claim 1 wherein the fluiddischarge member delivers a heated fluid, a cooled fluid, orcombinations thereof, to the surface area of a molten glass massoverflowing the at least one weir.
 4. The apparatus of claim 1 whereinthe fluid discharge member discharges a fluid from the fluid source toat least one location on the surface of molten glass overflowing the atleast one weir.
 5. The apparatus of claim 1 wherein the fluid dischargemember discharges a fluid in at least one direction, orientation, orboth, on the surface of molten glass overflowing the at least one weir.6. The apparatus of claim 1 wherein the fluid discharge memberdischarges a fluid that locally changes at least one of the temperatureproperties of the molten glass overflowing the weir; the flow propertiesof the molten glass overflowing the weir; the thickness properties ofthe molten glass overflowing the weir; or a combination thereof.
 7. Theapparatus of claim 1 wherein the fluid discharge member discharges afluid stream comprising a cross-sectional shape selected from at leastone of: a point; a small spot; a large spot; an oval, a non-symmetricalellipsoid or egg shape profile, a parabola, an hyperbola, a triangle orwedge shaped profile, a rectangle, or combinations thereof.
 8. Theapparatus of claim 1 wherein the fluid discharge member comprises atube, a pipe, an air knife, an air curtain, or combinations thereof. 9.The apparatus of claim 1 further comprising an enclosure thatsubstantially surrounds the at least one isopipe having at least oneweir and the fluid discharge member.
 10. A method for controlling theglass streams in fusion glass manufacture in the apparatus of claim 1,comprising: flowing molten glass over the at least one weir of the atleast one isopipe; and discharging a fluid from the fluid dischargemember in proximity to the at least one weir of the at least one isopipeonto the molten glass flowing over the at least one weir of the isopipe.11. The method of claim 10 wherein discharging a fluid from the fluiddischarge member situated above or atop the weir overflow isaccomplished selectively to at least one of: a specified location, aspot, a line, a region, or combinations thereof.
 12. The method of claim10 wherein discharging a fluid from the fluid discharge member comprisesdischarging an array of fluid discharge members that have the samespatial orientation and direction.
 13. The method of claim 10 whereindischarging a fluid from the fluid discharge member comprisesdischarging an array of fluid discharge members having at least onefluid discharge member having a different spatial orientation anddirection compared to the other fluid discharge members in the array.14. A method for controlling the glass streams in fusion glassmanufacture in the apparatus of claim 1, comprising: characterizing thethickness defect profile of a fusion glass manufacture product;determining at least one fluid discharge configuration that remedies thethickness defect profile, wherein the at least one fluid dischargeconfiguration comprises at least one of: the fluid flow rate andrelative temperature difference between the fluid and the glass stream;the orientation of the at least one fluid discharge member with respectto the inlet and compression ends of the isopipe; the location orproximity of the at least one fluid discharge member with respect to theinlet and compression ends of the isopipe; the geometry of the at leastone fluid discharge member; or combinations thereof and discharging thefluid from the at least one fluid discharge member to the at least oneweir of the at least one isopipe onto the molten glass flowing over theat least one weir of the isopipe in accordance with the characterizedthickness defect profile and the determined at least one fluid dischargeconfiguration.
 15. A method of forming a glass-glass laminate sheetcomprising: flowing a first molten glass over a first weir of a firstisopipe to form a first molten glass stream; flowing a second moltenglass over a second weir of a second isopipe to form a second moltenglass stream; forcing a fluid from a fluid discharge member in proximityto at least one of the first and second weirs such that the fluid isdirected onto the respective molten glass stream; fusing the first andsecond molten glass streams to each other to form a multilayerglass-glass laminate sheet.
 16. Use of the multilayer glass-glasslaminate sheet, made by the method of claim 15, as a cover glass or aglass backplane in an electronic device.
 17. Use of the multilayerglass-glass laminate sheet, made by the method of claim 15, in an LCDdisplay, an LED display, a computer monitor, an automated teller machine(ATM), a mobile telephone, a personal media player, a tablet computer, aphotovoltaic component, an architectural glass pane, an automotiveglazing, a vehicular glass, a commercial appliance, a householdappliance, or a solid state lighting article.
 18. An electronic devicecomprising a cover glass comprised of the multilayer glass-glasslaminate sheet made by the method of claim
 15. 19. An electronic devicecomprising a glass backplane comprised of the multilayer glass-glasslaminate sheet made by the method of claim
 15. 20. An electronic devicecomprising a display comprised of the multilayer glass-glass laminatesheet made by the method of claim
 15. 21. An architectural glass panecomprising the multilayer glass-glass laminate sheet made by the methodof claim
 15. 22. An automotive glazing comprising the multilayerglass-glass laminate sheet made by the method of claim
 15. 23. Avehicular glass member comprising the multilayer glass-glass laminatesheet made by the method of claim
 15. 24. An appliance comprising themultilayer glass-glass laminate sheet made by the method of claim 15.